3,204 research outputs found
Interaction of laser generated ultrasonic waves with wedge-shaped samples
Wedge-shaped samples can be used as a model of acoustic interactions with samples ranging from ocean wedges, to angled defects such as rolling contact fatigue, to thickness measurements of samples with non-parallel faces. We present work on laser generated ultrasonic waves on metal samples; one can measure the dominant Rayleigh-wave mode, but longitudinal and shear waves are also generated. We present calculations, models, and measurements giving the dependence of the arrival times and amplitudes of these modes on the wedge apex angle and the separation of generation and detection points, and hence give a measure of the wedge characteristics
Characterisation of the Medipix3 detector for 60 and 80 keV electrons
In this paper we report quantitative measurements of the imaging performance for the current generation of hybrid pixel detector, Medipix3, used as a direct electron detector. We have measured the modulation transfer function and detective quantum efficiency at beam energies of 60 and 80 keV. In single pixel mode, energy threshold values can be chosen to maximize either the modulation transfer function or the detective quantum efficiency, obtaining values near to, or exceeding those for a theoretical detector with square pixels. The Medipix3 charge summing mode delivers simultaneous, high values of both modulation transfer function and detective quantum efficiency. We have also characterized the detector response to single electron events and describe an empirical model that predicts the detector modulation transfer function and detective quantum efficiency based on energy threshold. Exemplifying our findings we demonstrate the Medipix3 imaging performance recording a fully exposed electron diffraction pattern at 24-bit depth together with images in single pixel and charge summing modes. Our findings highlight that for transmission electron microscopy performed at low energies (energies <100 keV) thick hybrid pixel detectors provide an advantageous architecture for direct electron imaging
Medipix3 Demonstration and understanding of near ideal detector performance for 60 & 80 keV electrons
In our article we report first quantitative measurements of imaging
performance for the current generation of hybrid pixel detector, Medipix3, as
direct electron detector. Utilising beam energies of 60 & 80 keV, measurements
of modulation transfer function (MTF) and detective quantum efficiency (DQE)
have revealed that, in single pixel mode (SPM), energy threshold values can be
chosen to maximize either the MTF or DQE, obtaining values near to, or even
exceeding, those for an ideal detector. We have demonstrated that the Medipix3
charge summing mode (CSM) can deliver simultaneous, near ideal values of both
MTF and DQE. To understand direct detection performance further we have
characterized the detector response to single electron events, building an
empirical model which can predict detector MTF and DQE performance based on
energy threshold. Exemplifying our findings we demonstrate the Medipix3 imaging
performance, recording a fully exposed electron diffraction pattern at 24-bit
depth and images in SPM and CSM modes. Taken together our findings highlight
that for transmission electron microscopy performed at low energies (energies
<100 keV) thick hybrid pixel detectors provide an advantageous and alternative
architecture for direct electron imagin
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Eyes on the bog. Long-term monitoring network for UK peatlands
Eyes on the Bog provides a scientifically robust, repeatable, low tech, long-term monitoring initiative.
The standardised methodology enables individual peatland sites to be consistently monitored across the UK, creating a network of comparable sites. The initiative employs cheap, simple techniques and modern technology to enable useful monitoring information to be collected by peatland community employees or volunteers on:
Peat subsidence and carbon loss
Carbon capture
Water table behaviour
Peat soil condition
Vegetation status, structure and composition
Historical context of change and current trajectorie
Rattus Model Utilizing Selective Pulmonary Ischemia Induces Bronchiolitis Obliterans Organizing Pneumonia
Bronchiolitis obliterans organizing pneumonia (BOOP), a morbid condition when associated with lung transplant and chronic lung disease, is believed to be a complication of ischemia. Our goal was to develop a simple and reliable model of lung ischemia in the Sprague-Dawley rat that would produce BOOP. Unilateral ischemia without airway occlusion was produced by an occlusive slipknot placed around the left main pulmonary artery. Studies were performed 7 days later. Relative pulmonary and systemic flow to each lung was measured by injection of technetium Tc 99m macroaggregated albumin. Histological sections were examined for structure and necrosis and scored for BOOP. Apoptosis was detected by immunohistochemistry with an antibody against cleaved caspase 3. Pulmonary artery blood flow to left lungs was less than 0.1% of the cardiac output, and bronchial artery circulation was ~2% of aortic artery flow. Histological sections from ischemic left lungs consistently showed Masson bodies, inflammation, and young fibroblasts filling the distal airways and alveoli, consistent with BOOP. In quantitative evaluation of BOOP using epithelial changes, inflammation and fibrosis were higher in ischemic left lungs than right or sham-operated left lungs. Apoptosis was increased in areas exhibiting histological BOOP, but there was no histological evidence of necrosis. Toll-like receptor 4 expression was increased in ischemic left lungs over right. An occlusive slipknot around the main left pulmonary artery in rats produces BOOP, providing direct evidence that ischemia without immunomodulation or coinfection is sufficient to initiate this injury. It also affords an excellent model to study signaling and genetic mechanisms underlying BOOP
Challenging the orthodoxy: union learning representatives as organic intellectuals
Teacher education and continuing professional development have become a key areas of controversy in England since the period of school sector restructuring following the 1988 Education Reform Act. More recently teacher training and professional development have often been used to promote and reinforce a narrow focus on the government’s ‘standards agenda’. However, the emerging discourse of ‘new professionalism’ has raised the profile of professional development in schools, and together with union learning representatives, there are opportunities to secure real improvements in teachers’ access to continuing professional development. This paper argues however that union learning representatives must go beyond advocating for better access to professional development and should raise more fundamental questions about the nature of professional development and the education system it serves. Drawing on Gramsci’s notion of the ‘organic intellectual’, the paper argues that union learning representatives have a key role as organisers of ideas – creating spaces in which the ideological dominance of current policy orthodoxy might be challenged
Effects of Intraventricular Locus Coeruleus Transplants on Seizure Severity in Genetically Epilepsy-Prone Rats Following Depletion of Brain Norepinephrine
Audiogenic seizures (AGS) in genetically
epilepsy-prone rats (GEPR) of the moderateseizure
substrain (GEPR-3s) were investigated
to determine whether norepinephrine (NE)
depletion induced by 6-hydroxydopalnine (6-OHDA)
microinfusion into the locus coeruleus
(LC) could alter the efficacy of intraventricular
NE tissue grafts in promoting reductions in
seizure severity in AGS. GEPR-3s were
stereotaxically infused with 6-OHDA
(4μg/side/rat), or vehicle into the region of the
LC. Following 6-OHDA treatment all animals
were subjected to 3 AGS tests. GEPR-3s seizure
severities were increased in 39.5% of the
animals after microinfusion of 6-OHDA into the
region of the LC. Following the third AGS test,
each rat was stereotaxicaily implanted with 17
gestational day rat fetal tissue obtained from the
dorsal pons and containing the primordia of the
LC or with tissue obtained from the neocortex
or were sham-grafted. Subsequent to grafting,
rats were subjected to 3 additional AGS tests.
53% (10/19) of 6-OHDA treated GEPRs showed
a significant reduction in seizure severity
following transplantation of fetal LC tissue. In
contrast, only 20% (1/5) of GEPRs infused with
saline rather than 6-OHDA showed, a reduction
of seizure severity following fetal LC
transplantation. NE content in the cortex and
pons/medulla was decreased by 78% and 46%
respectively following 6-OHDA microinfusion
into the LC. Prominent grafts with numerous
TH positive neurons and neurites were present
within the third ventricle of grafted animals,
while cortex grafts contained no TH
immunostained structures. These findings
suggest that the efficacy of fetal LC tissue to
promote reductions in seizure severity in GEPRs
is increased following depletion of central NE by
microinfusion of 6-OHDA
Attitudes to Reading and Writing and their Links with Social Mobility 1914-2014: An Evidence Review
This review has drawn on a range of literature, archive material, family interviews and data gathered using social media to explore attitudes to reading and writing and their links with social mobility from 1914 to the present day. It identifies the many ways in which families read for pleasure and identifies ways in which Booktrust’s activity might be developed
Direct detection of electron backscatter diffraction patterns.
We report the first use of direct detection for recording electron backscatter diffraction patterns. We demonstrate the following advantages of direct detection: the resolution in the patterns is such that higher order features are visible; patterns can be recorded at beam energies below those at which conventional detectors usefully operate; high precision in cross-correlation based pattern shift measurements needed for high resolution electron backscatter diffraction strain mapping can be obtained. We also show that the physics underlying direct detection is sufficiently well understood at low primary electron energies such that simulated patterns can be generated to verify our experimental data
Confirmation of co-denitrification in grazed grassland
peer-reviewedPasture-based livestock systems are often associated with losses of reactive forms of nitrogen (N) to the environment. Research has focused on losses to air and water due to the health, economic and environmental impacts of reactive N. Di-nitrogen (N2) emissions are still poorly characterized, both in terms of the processes involved and their magnitude, due to financial and methodological constraints. Relatively few studies have focused on quantifying N2 losses in vivo and fewer still have examined the relative contribution of the different N2 emission processes, particularly in grazed pastures. We used a combination of a high 15N isotopic enrichment of applied N with a high precision of determination of 15N isotopic enrichment by isotope-ratio mass spectrometry to measure N2 emissions in the field. We report that 55.8 g N m−2 (95%, CI 38 to 77 g m−2) was emitted as N2 by the process of co-denitrification in pastoral soils over 123 days following urine deposition (100 g N m−2), compared to only 1.1 g N m−2 (0.4 to 2.8 g m−2) from denitrification. This study provides strong evidence for co-denitrification as a major N2 production pathway, which has significant implications for understanding the N budgets of pastoral ecosystems.The authors are grateful for the funding that was provided through the Research Stimulus Fund Program administered by the Department of Agriculture & Food under the National Development Plan 2007–2013 RSF 07536. The first author is grateful for the funding provided by Teagasc through the Walsh Fellowship Scheme
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